Lottie and Rive portable animation/runtime models

Document status: reviewed. Canonical source.

Summary

Lottie specifies a JSON-based animated-vector document with extensible additional data. Rive serializes artboards, shapes, animation and state machines into a compact binary runtime format designed for forward evolution.

NUIF relevance

Animation/state-machine semantics should be modular rather than mixed into base geometry. NUIF should define stable behavior graph concepts and allow richer animation dialects to lower into them; it should not duplicate either runtime format wholesale.